Can you expand more on how the Prusa firmware works? From what I can see it has some special points on the bed that it locates carefully using an inductive sensor, and can then figure out how skewed the axes are. Does this match what you're talking about?

How would you do this without a special bed? I'm thinking perhaps that you could stick some bumps on the surface near the corners (carefully measured of course)?

Or are you just after some config variables to change the X/Y/Z scaling?

XYZ compensation (also called orhogonal axis compensation, or more accurately non-orthogonal axis compensation) isn't new. RepRapFirmware has supported it for more than 3 years.

What's new about Prusa's design is that he has some sort of markers in the bed that the inductive Z probe can detect, so that the XYZ compensation can be configured automatically instead of manually. If you are trying to mass-produce 3D printers and it's too hard or too expensive to get the mechanics moving at right angles, this is useful. If you are a hobbyist, it seems unnecessary to me. It's not hard to get the axes at right angles in most designs, and if you don't then manual configuration of the compensation can be used. Depending on how accurate the inductive sensing is, manual configuration of the compensation might be more accurate too.

Nope, the only thing i can see is the points in the code so it knows where they are

like you i assume it does search for them and then figures the skewness by comparing

"How would you do this without a special bed?"

I have found that the bed is not so special, it just have these 9 points where it triggers... outside the points the inductive probe will not trigger...

could it be done with a "normal" bed like the mk2.... maybe but then we would have to deal with changing the spots cords and stick something on the top of it that makes it trigger

and why bother? an pcb made on alu substrate can be made for about 35£ if getting 5 at a time

"Or are you just after some config variables to change the X/Y/Z scaling?"

ideal would be to get the bed produced as the source files specs and have a option to calibrate things just like prusa does.

downsidea to his hack of marlin is that it only seems to support one extruder. and again i will not go for marlin as my waste bin says no... i had way to many false triggers on the extruder temp. also a lot of times the thing just frezzes up either with the nozzle heating or sometimes it killed the heating... i have had none of that with repetier and simply since that works i live by the rule if its not broken dont try to fix it...

It seems quite clever. They are able to produce the bed to much tighter tolerances than everyone's random poorly built printer, so skewing the software to match the bed makes sense.

Are you trying to mass produce something, or correct a skew in your prints?

If the latter, check out axis compensation.

You need to

#define FEATURE_AXISCOMP 1

in your config file, and then it looks like you can set the XY axis skew in EEPROM using Repetier Host. From the looks of things you need to figure out the tan value of two measurements. You might need to do some digging to figure this out properly.

For the others reading this thread, please refresh your memory of the title, especially the bit that says "Repetier".

I think this is what is to be considered a dead horse... think i will just go for the design of the mk42 bed but without the 9 probe points... the 6 zoned heating is at least something better compared to the standard mk2 bed

Stupid.
So instead of printing a straight line, moving in only one axis, you'll print a stair step that approximates a straight line, because Prusa knows prosumers can't square up the axis worth doo-doo.
And if the bed isn't assembled square to the axis, the firmware will assume it is?, and "compensate" so your print is square with the little dots, in all 3 axis no less.
Great, now they can ship machines with bent rails, and it will be "okay".

Of course their bed is doing magic and not correcting, but so does all bed level stuff.

They have never corrected a problem but only compensated for it.

My idea was to be able to both compensate but also being told how far off the machine is so that you could correct it until the machine says it does not need correction... or until at least you get to where you cant correct it anymore without overshooting the ideal frame

I would be a bit wary of that because making heat beds is not as simple as sending the gerber files to a PCB fabricator. Getting the correct resistance and getting it flat enough consistently would be difficult I think.

Indeed, they shouldn't be plated. I'm wary of this campaign because he's talking about getting them in "2.4mm or maybe 3.2mm" - I think the real mk42 is 6mm FR4?. 3mm won't be stiff enough and will still need an aluminium plate which won't help with performance.

Correct me if I'm wrong, but the heatbed in the Prusa i3 MK2 uses a custom sensor that's much smaller than the normal inductive probes out on the market?

The 9 probe point I think are designed against their custom sensor, a larger sensor might work, but isn't going to be as accurate as their custom sensor considering the size difference of the sensing circle. So even having the MK42 heat bed isn't going to help unless you can pair it with their custom sensor with regards to the 9 probe points.

The heat zones might be an improvement, but the variheatbed from E3D's big box already has that readily available in the 300x200 size available for order. It does work very well too as I've got one fitted to one CoreXY printer I have at the moment.